Magnetically operated tool



Se t. 29, 1964 H. HORNSCHUCH ETAL 3,150,725

MAGNETICALLY OPERATED TOOL Filed July 13, 1961 2 Sheets-Sheet 1 l mm.

mvzmoas 36 4 HAN/VS wnuscwcn 2o JACK R. WEBB I as THEIR ATTORNEY H. HORNSCHUCH ETAL MAGNETI CALLY OPERATED TOOL Sept; 29, 1964 Filed July 13, 1961 2 Sheets-Sheet 2 INVENTORS HAN/V5 HORNSCHUGH JACK R. WEBB 5 Q THEIR TTORNEY United States Patent 3,150,725 MAGNETICALLY GPERATED TOOL Hanns Hornschuch, Easton, and Jack R. Webb, Bethlehem, Pa., assignors to Ingersoll-Rand Company, New York, N.Y., a corporation of New Jersey Filed July 13, 1961, Ser. No. 123,707 6 Claims. (Cl. 173-93) This invention relates to magnetically operated tools, and particularly to tools of this type adapted to deliver impacts for performing work.

A common application of this sort or" tool is found in so-called impact wrenches which are provided with an intermittently engageable chuck in which during disengagement one member gathers momentum to be expended upon the other member as an impact at reengagement. The member to which the impact is delivered is commonly called an anvil While the member delivering the impact is called the hammer.

There are various types of such clutches. In one type the hammer strikes the anvil with a glancing blow and in another type the hammer stops momentarily upon engagement with the anvil. The latter type of clutch is considered most effective since the hammer may be lighter as it delivers its full kinetic energy to the anvil at each blow.

This invention is particularly advantageous as applied to the second mentioned type of tool.

It is an object of this invention to improve the means by which the hammer element is caused to engage and disengage the anvil.

It is a further object of the invention to improve the effectiveness of the blow being delivered by the anvil to the work piece.

A still further object of the invention is to provide a very simple form of impact tool which shall be reliable, easily manufactured and easily manipulated by the operator.

Further objects of the invention and the advantages thereof will be in part obvious and in part pointed out hereinafter.

Preferred embodiments of the invention are illustrated in the accompanying drawings and here described.

In the drawing:

FIGURE 1 is a side view, partly in longitudinal section, of an impact wrench embodying the invention,

FIG. 2 is a perspective view of the anvil, hammer and its actuating member removed from the tool casing,

FIG. 3 is a longitudinal view partly in section of the elements included in FIG. 2,

FIG. 4 is a view similar to FIG. 2 with the addition of elements to produce the constant torque on the anvil in addition to that provided by the hammer,

FIG. 5 is a modified form of the invention as applied to an impact wrench, the view being partly in longitudinal section,

FIG. 6 is a longitudinal section through the hammer and anvil of the embodiment of FIG. 5,

FIG. 7 is an exploded perspective of the hammer, the anvil and actuating member of FIG. 6, parts being cut away to show the internal construction, and

FIG. 8 is a cross section through the hammer and its actuating element taken at the line 8-8 looking in the direction of the arrows.

Referring the drawing and more particularly to FIGS. 1-4 inclusive, the invention is illustrated as applied to an impact wrench in which it is desired to deliver blows in a rotary direction to an anvil member 10 which is provided with a suitable square coupling end 12 to receive a suitable working engaging element, such as socket wrench, screw driver blade, and the like, (not shown). Anvil 1t) constitutes the driven part of a clutch of which the driving element is a hammer 14. For interengagement, anvil 10 is provided with jaws 16 and hammer 14 has corresponding jaws 18. Jaws 16 are spaced apart and relatively narrow to provide space therebetween to permit rotational movement of jaws 18 therebetween, such movement being in this instance required for the hammer 14 to gather momentum before jaws 18 deliver their blows to anvil jaws 16. Both anvil 10 and hammer 14 are adapted to rotate and, in this instance, they are coaxial, hammer 14 being mounted on a stem 20 extending from anvil 10 in a rearward direction with reference to the end 12 which may be termed the front of the tool.

In accordance with this invention, hammer 14 is adapted to be magnetically actuated and to this end there is provided a rotational magnet member 22, coaxial with hammer 14 and anvil 10, adapted to turn continuously but not necessarily at constant speed to impart energy to hammer 14. Both of these members have magnetic pole faces juxtaposed with respect to each other and adapted to interact magnetically. Thus hammer 14 is provided with a plurality of pole pieces 24 of south polarity, as indicated, and pole pieces 26, alternating therewith, of north polarity. Similarly, actuating member 22 has a corresponding number of pole pieces 28 of north polarity alternating with pole pieces 30 of south polarity. Axially, hammer 14 and actuating member 22 are very closely spaced so that the maximum magnetic effect will exist therebetween.

A practical mounting for the elements as described above is indicated in FIG. 1, the various parts being housed Within a casing 32 having a nose portion 34 provided with a front bearing 36 for anvil 10 and a handle 38 by which the tool is to be manipulated. Within the casing 32 is housed a motor 40, which may be electrical or pneumatic, having a drive shaft 42 extending through a bearing 44 to be coupled to actuating member 22 mounted partly on drive shaft 42 and stem 20.

In this instance, hammer 14 and actuating member 22 are permanent magnets although it is obvious that they could be otherwise magnetized. Hammer 14 being permanently magnetized, jaws 18 may be formed of a separate portion 46 of material suitable for withstanding impacts. It is understood that member 46 will be attached by dowels 48 or otherwise to form a rigid portion of hammer 14. A bearing sleeve 50 on stem 20 is provided to take the wear due to rotation of hammer 14 with respect to anvil 10 and to reduce friction therebetween.

In operation of the aforedescribed tool, the tool is positioned to engage a member to be fastened, such as a screw, nut, stud, or the like, and the motor 40 operated to cause drive shaft 42 to rotate. Rotation of drive shaft 42 causes conjoined rotation of actuating member 22 by reason of the splined connection of the drive shaft with actuating member 22. Upon rotation of the magnetic actuating member 22, the attractive forces between its poles and the poles of hammer 14 of opposite polarity will rotatively entrain hammer 14 and cause the latter to rotate so that the jaws 18 of the hammer engage jaws 16 of anvil 10. With jaws 18 and 16 engaged, anvil 10 is rotated which, in turn, rotates the members to be fastened. In this rundown phase of operation of the tool, attractive forces between the unlike poles 24 and 28, 26 and 30 of the respective hammer 14 and actuating member 22 is sufficient to overcome the resistance to rotation imposed thereon by the member to be fastened and the slight frictional resistance to rotation between hammer 14 and anvil 1t) and between anvil 10 and casing 34 so that a direct drive exists and actuating member 22, hammer 14, and anvil 10 rotate as a unit whereby the advantages of high motor speed is achieved.

When the work or torque load on anvil 19 reaches a predetermined magnitude which exceeds the attractive magnetic forces between unlike poles 24 and 28, 26 and 30 of hammer 14 and actuating member 22, actuating member 22 is forced to rotate relative to hammer 14 by reason of its direct connection with motor 40, through drive shaft 42, and poles 24 and28, 26 and 30 will be forced to rotatively separate. In this impacting phase of operation of the tool, the continued rotation of actuating member 22 relative to hammer 14 will result in the like poles of hammer 14 and actuating member 22 passing each other, whereby the repulsive magnetic forces between the like poles, assisted by the attractive magnetic forces between succeeding unlike pairs of poles, will induce reverse rotation of the hammer (rotation counter to the direction of rotation of actuating member 22) relative to anvil 10. I Reverse rotation of hammer 14 carries jaws 18 of the hammer out of engagement with anvil jaws 16. The hammer 14 continues its reverse rotation until the attractive force between unlike poles on the hammer and actuating member overcomes the momentum in a reverse direction, at which time the hammer and actuating member become magnetically coupled together, as shown in FIG. 2, and the hammer is again rotated in a forward direction (same direction as actuating member 22). The hammer 14 is rotatively carried by actuating member 22 until hammer jaws 1'8 impact against anvil jaws 16. This impact is transmitted through anvil 1t) and the fastener engaging member (not shown) to the member to be fastened (not shown). Upon impact of hammer jaws 18 and anvil jaws 16, actuating member 22 is again forced to rotate relative to hammer 14 so that the unlike poles 24 and 28, 26 and 30 of the hammer and anvil angularly separate and the like and unlike poles on the respective hammer and actuating member alternately pass each other. As the like and unlike poles on the respective hammer 14 and actuating member 22 pass each other, the repellant and attractive forces therebetween, assisted this time by the recoil or rebound of the hammer upon impact, cause the hammer to rotate counter to the direction of rotation of the actuating member to thereby effect disengagement of the hammer jaws 18 and anvil jaws 16. The hammer 14 then reverses rotation, as previously described, with each hammer jaw until the forces between the unlike poles on the hammer and the actuating member overcome the momentum .of reverse rotation of the hammer and the unlike poles come into alignment, at which time the hammer again magnetically couples to actuating member 22 and is rotated in a forward direction to deliver another impact blow to anvil 10. The tool is operated as above described until the fastener (not shown is brought home. The forward and backward rotative motion, or oscillation of hammer member 14 with respect to anvil produces an angular velocity in hammer 14 much greater than that of the actuating member 22. Thus the impacting effect is much great than if hammer 14 would travel at the rotational speed of actuating member 22. Even when the hammer 14 and actuating member 22 are rotating at the same speed, if the poles are not aligned exactly alike or exactly opposite, a rotational force exists between the actuating member causing it to either accelerate or decelerate. Thus the hammer can be forced to go faster than the actuating member for a brief instant until the poles again align.

In this mechanism, an acceleration above actuation speed occurs by the following process: At impact of the hammer 14 and anvil 10, the actuating member continues in a forward direction and when like poles have just passed alignment, the hammer member is forced in a rearward direction.

Since the actuating member is still going in the forward directon, a pole change will again occur tending to reverse the hammer motion to the forward direction as the attractive force between unlike poles acts to retard the reverse rotation of the hammer. Because of the inertia of the hammer, this reversal does not occur instantane ously and the hammer poles lag the actuating member. The number of changes in polar relationship of the poles necessary to cause the hammer to cease reverse rotation and be rotatively picked up by the actuating member is dependent upon the torque load on the anvil at a particular impact stroke, the inertia of the hammer, and the inertia of rotation of actuating member 22. For example, if a high torque load exists so that upon impact the anvil is rotated only slightly, the relative rotation of the actuating member with respect to the hammer will be substantially great with a relatively large number of polar changes occurring before the hammer again is picked up and rotated forwardly to deliver another impact blow. Even when they reach the same forward speed, this misalignment or lag provides a force to accelerate the hammer to proper alignment with the actuating member and the hammer therefore travels faster than the actuating member for this brief period as the hammer is carried toward delivery of another impact blow. It is during this time that impact with the anvil is made to occur to utilize this advantage. It is to be understood that the blow imparted by the jaws 18 is proportional to the square of the velocity of hammer 14 at the moment of impact.

In many tools of this character a great deal of energy is lost by looseness of the workpiece, as for instance the socket at its coupling with the anvil 10. This is partly due to energy loss in accelerating the hammer to take up the looseness. The damping effect is a very considerable loss. This construction lends itself to the use of a very convenient form of snubber. By this invention, actuat ing member 22 is caused to produce a slight snubbing torque in anvil 1d of a constant value. On stem 20 is mounted a sleeve 52 of magnetic material although not permanently magnetized adapted to rotate therewith. This sleeve 52 is adapted to cut the lines of force in the field between pole pieces 28 and 3t) and is thereby entrained to produce a torque in the direction of rotation of actuating member 22. The torque thus produced is not of a great degree so that an undue load on motor 46 is not produced thereby. However, the torque is sufficient to cause tightness at the coupling end 12 at the moment of contact of jaws 18 with anvil jaws 16.

A modified form of the invention is shown in FIGS. 5-8 inclusive. In this embodiment anvil 10 is adapted to be engaged by jaws 19 carried by hammer 15 rotatable on stem 21 of anvil 10. As best shown in FIG. 8, hammer 15 is hollow being provided with a bore 54 which forms its magnetized pole face, the north and south poles alternating as indicated by the reference characters N and S, N being a north pole and S being a south pole. The actuating member 23 is rotatably mounted on stem 21 and is cylindrical, its periphery 56 being magnetized, also as shown in FIG. 8, and indicated by the poles N and S. The clearance between bore 54 and the periphery 56 of actuating member 23 should be very slight to cause the same magnetic interaction above described in connection with the other embodiment. This arrangement has the advantage of being slightly more compact inasmuch as actuating member 23 fits within hammer 15. The general arrangement is shown in FIG. 5, there being provided a housing 33, a forward extending portion 35 which houses hammer 15, anvil 1t! and motor 41 driving actuating member 23 through shaft 43. A suitable handle 39 is provided for manipulation of the complete tool. The operation of the tool according to this embodiment is the same as described with respect to the embodiment illustrated in FIGS. 1 to 4.

Thus, by the above construction are accomplished, among others, the objects hereinbefore referred to. 7

We claim:

I 1. An impact tool comprising a rotary anvil having blow receiving jaws, a rotary hammer adapted to deliver blows to said jaws, said hammer having magnetic north and south poles alternating, an actuating member for said hammer rotatable with respect thereto and having corresponding poles juxtaposed to the hammer poles, and means magnetically cooperative with said actuating member and independent of said hammer to bias said anvil in the direction of rotation of said actuating member.

2. An impact tool comprising a rotary anvil having blow receiving jaws, a rotary hammer adapted to deliver blows to said jaws, said hammer having magnetic north and south poles alternating, an actuating member for said hammer rotatable with respect thereto and having corresponding poles juxtaposed to the hammer poles, and a member drivingly attached to said anvil and magneti cally associated with said actuating member to impart constant torque to said hammer.

3. An impact tool comprising a rotary anvil having blow receiving jaws, a rotary hammer adapted to deliver blows to said jaws, said hammer having magnetic north and south poles alternating, an actuating member for said hammer rotatable with respect thereto and having corresponding poles juxtaposed to the hammer poles, and a member carried by said anvil drivingly attached thereto and magnetically associated with said actuating member to impart constant torque to said hammer.

4. An impact tool comprising a rotary anvil having blow receiving jaws, a rotary hammer adapted to deliver blows to said jaws, said hammer having magnetic north and south poles alternating, an actuating member for said hammer rotatable with respect thereto and having corresponding poles juxtaposed to the hammer poles, and a member of magnetic material drivingly attached to said anvil and carried thereby and magnetically associated with said actuating member to impart constant torque to said hammer.

5. In an impact tool for rotating a fastening means relative to another member, the combination comprising an anvil drivably supported for rotation and adapted to engage a fastening means, a hammer disposed to engage said anvil to rotate the latter, a driving member coextensively arranged with respect to the hammer and connected for rotation to a source of rotary power, said hammer and said driving member each having magnetic means for coupling the hammer and the driving member together for conjoined rotation, and means magnetically cooperatively associated with the magnetic means of said driving member and cooperatively associated with said anvil to bias said anvil in the direction of rotation of said driving member to maintain the anvil against the fastening means.

6. In an impact tool for rotating a fastening means relative to another member, the combination comprising an anvil drivably supported for rotation and adapted to engage a fastening means, a hammer disposed in coaxial relationship to said anvil and constructed and arranged to engage said anvil to rotate the latter, a driving member coextensively arranged with respect to the hammer and connected for rotation to a source of rotary power, said hammer and said driving member each having magnetic elements for coupling the hammer and driving member together, and means connected to said anvil and magnetically cooperatively associated with the magnetic elements of said driving member to bias said anvil in the direction of rotation of said driving member to maintain the anvil against the fastening means.

References Cited in the file of this patent UNITED STATES PATENTS 2,471,947 Giannini May 31, 1946 2,481,360 Sprenger Sept. 6, 1949 2,691,434 Jimerson Oct. 12, 1954 2,898,791 Maurer Aug. 11, 1959 2,929,477 Rodriguez Mar. 22, 1960 2,943,216 Spodig June 28, 1960 

1. AN IMPACT TOOL COMPRISING A ROTARY ANVIL HAVING BLOW RECEIVING JAWS, A ROTARY HAMMER ADAPTED TO DELIVER BLOWS TO SAID JAWS, SAID HAMMER HAVING MAGNETIC NORTH AND SOUTH POLES ALTERNATING, AN ACTUATING MEMBER FOR SAID HAMMER ROTATABLE WITH RESPECT THERETO AND HAVING CORRESPONDING POLES JUXTAPOSED TO THE HAMMER POLES, AND MEANS MAGNETICALLY COOPERATIVE WITH SAID ACTUATING MEMBER AND INDEPENDENT OF SAID HAMMER TO BIAS SAID ANVIL IN THE DIRECTION OF ROTATION OF SAID ACTUATING MEMBER. 